The present invention relates to a high speed, high performance facsimile apparatus which has an image data storing function.
Prior art facsimile systems have generally been constructed with either one of two different designs, one directed toward cutting down cost and size and the other toward enhancing speed and performance. A low cost, small size facsimile apparatus is usually provided with a single processing unit (microprocessor) which executes various kinds of control and processing including compression and restoration of image data, sequence control, exchange of data through input/output ports, exchange of image data through an image recorder (plotter) and an image reader (scanner), communication protocol control, and operator interface control. A high-speed and high-performance apparatus, on the other hand, is provided with a plotter, a scanner, a data compression/restoration unit and a communication control unit which are constructed separately from each other. All these independent units are controlled by a processing unit, while input and output image data are processed and transferred by another hardware without the intermediary of the processing unit. For example, concerning the sequence control over various structural elements of a facsimile apparatus, it is executed by a processing unit and the transfer of image data between the elements is implemented with an exclusive high-speed transfer bus or with hardware which interconnects the elements, in the latter case the bus connection to the processing unti being omitted. Such makes the overall construction of the apparatus complicated and bulky. In an apparatus using a certain prior art system, input and output of image data to and from a data compression/restoration unit is accomplished using a hardware interface and, therefore, definitely determined in configuration at the stage of hardware design, thus lacking flexibility in meeting a particular application. That is, with such an apparatus, it is impossible to flexibly change the sequence and frequency of image data transfer between the structural elements for matching them to a particular system application. Stated another way, it is difficult to use the apparatus for multiple purposes and, therefore, the system lacks vertatility.
Meanwhile, a type of high-speed, high-performance facsimile system known in the art is furnished with a store and forward (SAF) function for storing and then transmitting image data. In the event of reception of image data, the SAF type facsimile apparatus temporarily stores received image data in an image data store area and allows them to be outputted as a hard copy afterwards through a recorder. Generally, facsimile communications are set up based on any of communication systems which are described in CCITT Recommendations, e.g. GIII communication system. While a facsimile apparatus operates as a receiving station, it sends a digital identification signal (DIS) back to a transmitting station as an initial identification signal. As well known in the art, the signal DSI serves to inform the transmitting station of the performance particular to the receiving station, the performance including the minimum transmission time specific to the transmitting station. The minimum transmission time is defined as a transmission time necessary for transmitting one scanning line of image data.
A prior art facsimile apparatus, even if provided with the SAF function, has customarily been designed to inform a transmitting station of a hard copy outputting rate of its recorder as the minimum transmission time. This gives rise to a problem that since the outputting rate of a recorder in general is far slower than the writing rate of a memory and, therefore, it is quite probable that the store area for the temporary storage of received image data becomes partly emptied, the reception of image data is restricted by the slow output rate of the recorder. Such has obstructed fast and efficient transmission of image data.